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Biomedical subjects

S Clark

Publications and source records attributed to S Clark.

At least 163 records · Page 9Linked to original sources
PubMed1996

Reduced cell attachment and phosphorylation of focal adhesion kinase associated with expression of a mutant insulin receptor.

Insulin signaling results in rapid changes to the cell cytoskeleton, and it has recently been shown that insulin stimulates the dephosphorylation of the cytoskeletal-associated tyrosine kinase, focal adhesion kinase (pp125(FAK)). We report here that mutation of two tryptic cleavage sites (Lys164 and Lys582 --> Asn; 2N) in the insulin receptor alpha-subunit results in a cell-line (CHO.2N-10) with altered morphology associated with an increase in cell size, a decrease in cell adhesiveness, and a decrease in pp125(FAK) tyrosine phosphorylation in the absence of insulin (45.2 +/- 9.7% compared to nontransfected Chinese hamster ovary (CHO) cells). In contrast to pp125(FAK), paxillin phosphorylation was similar in all cell lines despite lower levels (61.0 +/- 10.4% compared to CHO cells) of paxillin protein in CHO.2N-10 cells. We observed comparable protein levels of pp125(FAK) and the structural focal adhesion protein, vinculin, in all cell lines. Despite underphosphorylation of pp125(FAK) in the basal state, insulin stimulation of CHO.2N-10 cells still resulted in dephosphorylation of pp125(FAK). CHO.2N-10 and CHO.T (overexpress wild-type insulin receptor) cells have similar insulin binding characteristics, insulin-stimulated autokinase and peptide phosphorylation, and insulin-stimulated pp185/IRS-1 phosphorylation. Our results suggest that the insulin receptor may play an important role in cell-matrix interactions, such as modulating cell adhesion and inducing cell architecture changes.

Amino Acid Sequence↗
PubMed1996

Proximal promoter elements of the human zeta-globin gene confer embryonic-specific expression on a linked reporter gene in transgenic mice.

We have investigated the transcriptional regulation of the human embryonic zeta-globin gene promoter. First, we examined the effect that deletion of sequences 5' to zeta-globin's CCAAT box have on zeta-promoter activity in erythroid cell lines. Deletions of sequences between -116 and -556 (cap = 0) had little effect while further deletion to -84 reduced zeta-promoter activity by only 2-3-fold in both transiently and stably transfected erythroid cells. Constructs containing 67, 84 and 556 bp of zeta-globin 5' flanking region linked to a beta-galactosidase reporter gene (lacZ) and hypersensitive site -40 (HS-40) of the human alpha-globin gene cluster were then employed for the generation of transgenic mice. LacZ expression from all constructs, including a 67 bp zeta-globin promoter, was erythroid-specific and most active between 8.5 and 10.5 days post-fertilisation. By 16.5 days gestation, lacZ expression dropped 40-100-fold. These results suggest that embryonic-specific activation of the human zeta-globin promoter is conferred by a 67 bp zeta-promoter fragment containing only a CCAAT and TATA box.

Animals↗
PubMed1996

Delineation of 7q11.2 deletions associated with Williams-Beuren syndrome and mapping of a repetitive sequence to within and to either side of the common deletion.

The majority of Williams-Beuren syndrome (WBS) patients have been shown to have a microdeletion within 7q11.2 including the elastin gene locus. The extent of these deletions has, however, not been well characterized. Thirty-five deletion patients were tested for all polymorphic markers in the 7q11.2 region bounding ELN to define the extent of deletions associated with WBS. With only one exception, ELN, D7S1870, and one copy of the D7S489 locus (D7S489U) were always included in the deletions. One patient showed lack of maternal inheritance at D7S1870 and not at ELN or D7S489U. A product corresponding to D7S489U was amplified from YAC 743G6 and from the P1 clone RMC07P008, thereby localizing both to within the common deletion. The boundary of the deleted region on the proximal (centromeric) side is D7S653 and on the distal side is D7S675, neither of which were ever included in the deletion. One locus, D7S489L, was variably deleted in patients, indicating a minimum of two common breakpoints on the proximal side. At least one additional repeat amplified by D7S489 (D7S489M) was localized to a YAC contig mapping distal to the common deletion. The D7S489 sequence is highly homologous to several cDNA clones in the GenBank database and contains an Alu sequence. It is possible that this andsolidusor other repetitive sequences in this region could play a role in the mechanism of deletion.

Base Sequence↗
PubMed1996

Insulin and insulin-like growth factor-1 stimulate dephosphorylation of paxillin in parallel with focal adhesion kinase.

Paxillin and focal adhesion kinase (pp125FAK) co-localize in focal adhesions; recently insulin has been shown to stimulate the dephosphorylation of pp125FAK; however, its effect on paxillin is unknown. We show that insulin and IGF-1 can stimulate the dephosphorylation of paxillin in CHOT (overexpress human insulin receptors) and CHO delta CT69 (overexpress insulin receptors lacking C-terminal 69 amino acids) cells. Furthermore, the insulin-receptor C-terminus is not needed for either insulin or IGF-1 to stimulate paxillin or pp125FAK dephosphorylation in the CHO (Chinese-hamster ovary) cell lines used.

Animals↗
PubMed1996

The uncoupling of Shc activation from distal intracellular signalling in a cell line which expresses a truncated human epidermal growth factor receptor.

We have examined epidermal growth factor (EGF) signalling in a CHO cell line (CHO11) which expresses a human EGF receptor truncated at amino acid 990. Previous studies showed that EGF treatment of these cells failed to increase prostaglandin production or phospholipase A2 activity. In the current study EGF increased the tyrosine phosphorylation of the intracellular signalling protein Shc in CHO11 cells but did not activate either of the downstream signalling enzymes raf or mitogen activated protein kinase (MAPK). The uncoupling of Shc activation from distal signalling in CHO11 cells contrasts with other cells which express similar mutant EGF receptors. The failure of She to activate distal signalling may reflect qualitative differences in the way that this protein is activated or could result from the activation of an inhibitory signalling pathway.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Association of cyclin-dependent kinase-4 and cyclin D1 in neonatal beta cells after mitogenic stimulation by lysophosphatidic acid.

Neonatal pancreatic islet beta cells retain a mitogenic capacity in response to growth factors. In this study an increased incorporation of 5-bromo-2'-deoxyuridine in response to oleoyl-lysophosphatidic acid is preceded by a GTP-dependent increase in phosphorylation of the extracellular signal-related kinase, ERK1. The presence of cyclin-dependent kinase-4 and an association with a catalytic partner cyclin D1, a process by which the progression through the cell cycle is regulated in other cell types, was shown to follow this. The mechanisms linking ERK1 phosphorylation and activation of cell cycle progression are not known. Investigation of this process in neonatal beta cells may provide a common pathway for the early response to growth factors and the conditions required for an increase in beta cell mass by proliferation.

Animals↗
PubMed1996

Analysis of failure in medical abortion.

Medical abortion opens a new choice to women wishing to terminate a pregnancy. Increasingly, providers in the developing and developed world will begin to offer this option. Yet, the nomenclature and concepts used for measuring failure of surgical abortion are not directly adaptable because of important differences inherent in the method and in the way it is offered in a given setting. We propose that failures in medical abortion should be defined as a surgical intervention (whether vacuum aspiration or dilatation and curettage) performed for any reason. Such instances may be further classified into three types: user choice interventions, provider choice or error interventions, and true drug failures requiring intervention. Further description and examples of each type are given.

Abortifacient Agents↗
PubMed1996

Schizophyllum commune: an unusual isolate from a patient with allergic fungal sinusitis.

We describe the first case of allergic fungal sinusitis (AFS) associated with Schizophyllum commune. Histological diagnosis was made on the mucinous material from the sinus which contained eosinophils, fungal hyphae and Charcot-Leyden crystals. The fungal isolate was identified as S. commune on the basis of its colonial morphology and minute peg-like outgrowths from vegetative hyphae and clamp connections. The optimal treatment of AFS is not known but may involve surgical debridement followed by systemic corticosteroids, gradually reduced, with the patient being maintained on inhaled corticosteroids. Oral itraconazole could be added to the regimen of those patients in whom frequent recurrences occur after debridement or when there is histological evidence of severe pressure erosion.

Adult↗
PubMed1996

Production of hyaluronan by glomerular mesangial cells in response to fibronectin and platelet-derived growth factor.

The formation of the non-sulphated glycosaminoglycan hyaluronan by cells of the renal glomerulus in diabetes may contribute to altered matrix composition. We describe an increased production of hyaluronan from mesangial cell-enriched glomerular cores from diabetic animals, and further show that increased hyaluronan production follows the exposure of non-diabetic and diabetic preparations to fibronectin and to platelet-derived growth factor in vitro. Hyaluronan production appeared dependent on protein kinase C activity, and could not be shown after prolonged phorbol ester preincubation. Stimulation by fibronectin was wholly dependent on cyclooxygenase activity and prior prostaglandin production, while the effect of platelet-derived growth factor showed only a partial dependence.

Animals↗
PubMed1996

Improved quality of life in patients with generalized cardiovascular metabolic disease on a prepared diet.

Current dietary recommendation for cardiovascular disease risk reduction and recommended dietary allowances (RDAs) were used to develop a nutritionally complete prepackaged prepared meal plan specifically designed to reduce the risk of cardiovascular disease. In the current study we tested patient acceptance of the diet as defined by measures of quality of life. In a randomized, parallel-design, multicenter clinical trial, 77 persons with hypertension, diabetes mellitus, dyslipidemia, or a combination of two or more of these conditions were recruited and randomly assigned to either a prepared meal plan (n = 39) or a comparable self-selected diet (n = 38) for 10 wk. The prepared meal plan met both the RDAs for all essential micronutrients and the dietary recommendations of national health organizations for macronutrients, cholesterol, sodium, and fiber. The prescribed self-selected diet was matched for macronutrients. Quality of life, as measured by a battery of instruments, was the major endpoint. Individuals consuming the prepared meal plan had significant improvements in mental health (P < 0.01), general perceived health (P < 0.005), daily activities (P < 0.05), work performance (P < 0.005), affect (P < 0.01), and nutritional health perceptions (P < 0.001), and reductions in nutrition hassles based on a standardized questionnaire (P < 0.001). The self-selected-diet group had significant improvements in nutritional health perceptions (P < 0.001) and affect (P < 0.001). There were significant improvements in weight (P < 0.001), blood pressure (P < 0.001), cholesterol (P < 0.002), low-density lipoproteins (P < 0.001), glucose (P < 0.014), and glycated hemoglobin (Hb A(1c) (P < 0.004) that were comparable in both groups. In summary, this study shows that a nutritionally complete diet, whether prepackaged or self-selected, improves multiple risk factors for cardiovascular disease. The prepackaged prepared meal plan had the added benefit of a greater improvement in quality of life.

Blood Glucose↗
PubMed1996

MMPI performance of central American refugees and Mexican immigrants.

This study compared the MMPI scores of Central American refugees from Guatemala and El Salvador to those of Mexican immigrants. It was expected that subjects from Guatemala and El Salvador would obtain higher scores on the F, D, Pa, and Sc scales because these subjects came from "war-torn" countries. A multivariate analysis of variance yielded no significant differences between the three groups on any of the validity and clinical scales including F, D, Pa, and Sc. Recommendations for cross-national research are noted especially in light of the new version, or MMPI-2.

Adult↗